Compressor



a. s. AIKMAN 1,773,717

COMPRESSOR Filad April 22, 1927 3 Sheets-Sheet 2 Aug. 26, 1930.

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' B s, AIKMAN COMPRES S OR Filed mi 22. 1927 s Shee'ts-Sheet s Patented Aug. 26, 1930 entree star s Parana rarer:

BURTON S. AIKMAN, F MILWAUKEE, WISCONSIN, ASSIGNOR T0 NATIONAL BRAKE & ELECTRIC COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN COMPRESSOR Application filed April 22,

My invention relates to gas compression, and more particularly to the type disclosed in my prior Patent #l,611,866 in which themlet valve comprises asleeve. lVhereas, in

the compressorshown in my aforesaid patent the sleeve valve is actuated solely by ring friction, according to the present invention dependence need not be placed solely upon ring friction, but may be supplemented by mechanical actuation, or replaced entirely by such mechanical actuation.

In the development of a high speed compressor, i. e., a compressor adapted for continuous operation at high speed, the first re quirement for eflicient operation is adequately rapid and efficient valve action. This refers particularly to inlet valve operat1on, butextends also to. discharge valve operation.

I am aware that compressors having mechanically actuated poppet valves have been produced and that rotary valves have been n'ovided, but I believe that prior to my recent development of the sleeve valve com-' pressor, originated by Renault (French Patent n e r2521), there has been no compressor on the market capable of continuous commercial operation at high speed. According to the present invention I provide means for m chanical actuation of the Valve sleeves shown in my aforesaid patent. For small size compressors operating at high speed the actuation by ring friction is adequate and highly successful. For larger sizes the weight of the sleeveincreases moreurapidly than does the ring friction, so that it is de sirable to supplement the actionof ring friction mechanical actuation.

In the preferred form of my present invention the sleeve is opened and closed at its upper end by longitudinal motion of small traverse. The sleeve is a straight cylinder guided at its upper and lower ends; The valve seat which co-operates with the upper end of the sleeve is. a thin annular spring metal plate clamped and seated against the bottom of the head along itsouter margin and at its inner margin overhanging a shale low groove, which. communicates with the compression space of, the cylinder. This plate has sufiicient flexibility to form a good 1927. Serial No. 185,713..

seal with the upper end of the sleeve sincethe pneumatic pressure on the upper side of the plate presses it against the edge of the sleeve. The effective area of the plate may be controlled to givethe desired pressure.

The sleeve is connected to a suitable cam actuated member operated by a cam driven Two cylinders may be operated by the same cam mechanism since they operate at 180 difference. p I

The ring friction in the present instance assists in moving the sleeve in the proper direction on both opening and closing so that normally all that the cam mechanism needs to do is to hold the valve closed or open after it has been moved to position by the ring friction. Where the seating or sealing ring has greater effective area than the upper end of the sleeve, the cam mechanism is required to sustain the differential pressure thus produced.

Preferably, but not necessarily, thecam follower is spring actuated in one direction and positivelyactuated' by the cam in an-' other.

While this form of compressor 'iscapable of operation at full motor speed, particularly in smaller sizes, 1t 1s of especial utility in larger sizes and at lower speeds, as when not intended to limit the invention'thereto as the valve may be a separate sleeve.

A further feature of my invention is an improved unloader, preferably of the type disclosed in prior Patent No. 1,400,133, but adapted to the particular mechanism herein employed. In the preferred form of my compressor I employ an air blower to cool the sleeve and head, scavenge the cylinder, and supercharge the same. The blower should operate a relatively high peripheral s need and it is desirable to use a relatively small diameter but large displacement blower. For this purpose the blower shaft is geared up. I utilize the gears as a gear pump to pump oil to the bearings under forced feed, and to operate a loading cylinder under the control of the receiver pressure. While in the preferred embodiment .I show a rocking lever for actuating or holding the valve sleeves to and away from their seats, and while I cause the unloader to act upon a pivot of said lever, I do not intend to limit the invention to this particular embodiment. The present invention provides certain other features of invention which will be.

more particularly pointed out and defined in the following specification and claims.

Now, in order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, I shall describe in connection with the accompanying drawings a specific em- 20 bodiment of the same.

25 Fig. 2 is a vertical longitudinal section through the compressor showing one of the valves in elevation;

Fig. 3 is an end view of the compressor with the end cover plate removed;

Fig. 4: is a fragmentary sectional view of the valve operating cam and lever connection;

Fig. 5 is a fragmentary end view of the oil pump shown in section in Fig. 2; and

35 Fig. 6 is an enlarged detail section of the seating plate.

Referring first to Fig. 1, the compressor 1 is shown with a discharge or delivery pipe 2 leading to the receiver 3 and from thence by pipe 4 to the point or points of consumption of the compressed gas.

A controller 5 is connected by pipe 6 to the receiver 3 and is adapted, when the desired maximum pressure has been attained in the receiver 3, to admit compressed air by way of the pipe 6 to the pipe 7, and thence to the unloading controlcylinder 8, which contains a piston 9 for operating an unloading control valve 10 to be described later. When the pressure in the receiver 3 drops to a predetermined minimum, the controller 5 cuts off compressed air from the pipe 7 and connects the same to atmosphere by way of the vent pipe 11. The compressor comprises a cylinder and crank case casting 12 carrying the cylinder on the upperhalf of the crank case, and a base casting 13 which forms the lower half of the crank case and also a mounting base with suitable boltinglugs 14 to for mounting the compressor on a foundation.

Ahead casting 15 is bolted by suitable companion flanges to the upper end of the cylinder casting 12. The castings 12 and 13 are joined on the line of the crank shaft 16 by suitable clamping flanges 17. The crank shaft 16 extends out through the end of the base 13 through an opening 18 which is normally closed by a cover member 19 provided with suitable felt washers, or like gaskets, to keep the oil which is on the crank shaft from escaping out along the surface or the crank shaft. The base member 13 is hollow to provide storage space for a relatively large body of lubricating oil. The crank shaft 16 shown herein is a two throw shaft having the cranks 20 and 21 provided with suitable connecting rods 22 and 23. The base 13 contains webs 24 and 25 providing a central bearing 26 between the throws of the crank shaft and an end bearing 27 inside the case 13. These webs 24 and 25 are provided with openings 28, 29 through which the oil may flow freely.

At the other end of the base member 13 there is mounted the frame or bracket member 30 for supporting the blower 31. This blower is preferably of the Sturtevant or squirrel cage type having an air inlet at 32 opening into the interior of the rotor which is not shown, and a delivery pipe 33 leading up to the cylinder casting 12 and opening into a port 34 on one side of the cylinder casting 12. The bracket 30 contains a suitable clamping flange 35 for clamping the bracket to the base and to the cylinder casting, and it contains also a sleeve 36 which supports the pump casing and the blower shaft. The blower shaft 37 has hearings in the extended sleeve portion 33 which lies inside of the tubular portion 36 of the bracket 30. At the inner end the blower shaft 37 has a pinion 39 meshing with a pinion 10 bolted onto the end of the crank shaft 16. The casing for the gear pump comprises two parts, the inner half 41 and the outer half 12, which are suitably bolted together with companion flanges, and both are supported by the tubular extension 38 forming a part of the housing part 12. The rear housing part 42 has a dome 13 connected by discharge pipe 1 1 (see Fig. 5) to the discharge side of the gear pump to receive oil under pressure therefrom, and it has a delivery connection 45 leading to the unloader cylinder 46 and to the pressure release valve cylinder 47.

The crank shaft 16 is drilled by generally longitudinal drilling 50, this drilling 5O having connections leading to the bearings 26, 27 and 51 and, in addition, it has connections leading to the drilling through the connecting rods 22 and 23 in a manner which is well understood by those skilled in the art. The drilling 52 through the connecting rod 22 is shown in Fig. 2 and it leads oil from the groove 53 to the wrist-pin bearing 51in pis- 15:

ton 55.

The piston 55 works in the cylindrical sleeve 56, the upper end of which, in conjuno tion with the valve seat formed by the plate 89, later to be described, forms the intake mechanism provided in conjunction withthe sleeve valve. The valve sleeve 56 is provided with a boss 57 (see Figs. 3 and a) from which a pin 58 projects, this pin passing through a lever 59 by which the motion of the sleeve is controlled through cam mechanism. The outer end of the lever 59 is connected by a clevis 60 to a thrust rod 61.

The thrust rod 61 has a collar 62, preferably formed integral therewith, between which collar 62-and a web 63 there is provided a compression spring 64 tending thereby to pull the forward end of the lever 59 downwardly. The lower end of the thrust rod 61 is connected to the forked rocking lever 65 by a pivotal connection 66. The other end of the lever is connected by a pivotal connection 67 to a stationary lug 68 provided on the inside of the cylinder frame casting 12.

Between the two sidesof the lever 65 there is disposed the. cam follower. 70 which, in this case, comprises a roller mounted through a ball bearing 71 on a cross pin 7 2. The periphery ofthe roller 70 rides upon the periphery of the cam 73. This cam 73 is preferably formed as anintegral part of the crank shaft 16. The-cam has a raised portion which extends for 180 and a relatively depressed portion which extends for the other 180 this cam having a very small throw only.

The lever 59 has a pivotal conne'ctionon the pin 74 connected by a yoke or clevis 76 to a piston rod 77, which has the piston 7 8 mounted in the unloading cylinder 46 and adapted to engage. the upper head 79011 its upper limit of traveland the stop 80 on its lower limit of travel. A compression spring 81 is contained within the hollowopiston and it tends to depress this pistonagainstthe stop 80 at all times. V V

The piston rod 23 has a piston like piston55 playing in the sleeve 82, which in all respects is likesleeve56, but arranged at all times to be 186? out of phase with the sleeve 56.

The lever 59 has a pin connection, such as that described in connection with Figs. 3 and 4, so'that the two sleeves, namely,56 and 82 are connected at equi-distant points from the pivot pin 74 on the lever 59. Hence, as the cam 78on'the crank shaft 16 operates'the cam follower 70 and hence the lever system, the sleeves 56 and 82 arerocked up and down, respectively, or vice 'versa. V

The web 68 forms guides for the lower ends of the valve sleeve 56, this web 63 extending: across the lower end of thecylinder portions of the casting 12 to define an air box having an inlet at the inlet port 3% and an outlet at the openlng 83 which is covered by the duct 8% terminatin in nozzle 85 directed u on the discharge valve box or chamber 86 to which the dischar e pipe 2 is connected.

Thus a plenum box 86 1S formed 1n the upper part of the casting 12 between the web 63 and the head 15 and surrounding the valve sleeves 56 and 82. The front part of the plenum chamber 86 has an opening which is normally closed by a removable plate 87 which gives access to the valve mechanism as shown in Fig. 3. r

The sleeves 56 and 82 are guided in suitable guiding rings 88 secured on the under side ofthe head 15:, these guiding rings guiding the upperends of the sleeves 56 and 82 into and out of engagement with the spring plates 89 forming'valve seats for the upper ends of the sleeves 56 and 82, which upper ends of the sleeves are out of? sub stantially square. The rings 88 clamp the thin annular plates 89 over annular recesses 90'Wl1lCll are overhung by the inner edges of the plates 89 so as to form a pneumatically held seal with the upper ends of the sleeves.

The rings88 have clamping flanges 91 lying in recesses formed in the bottom of the head member 15 to clamp the plates 89 and to support the bearing parts of the rings 88 within which the valve sleeve 56 plays. A. series of ports 92 are formed through the side walls of the rings so as to: permit air from the plenum box to be forced in to the cylinder to cool the same and to super-chargethe same when the sleeve is inthe low-er position as shown at 56 in Fig. 2. Whereas, ring friction of the piston 55 might be suflicientto shift the valve 56 and does operate to assist the positive mechanical means for'shifting this valve, it insures proper operation of the sameat all times. p

It will be observed, for example, inFig.

6', that the overhanging edge of the-seat formed by the plate, 89 is subject to internal" pneumatic pressureduring compression, and this overhanging area is available to apply pressure'to the plate 89, forcing it against the, upper edge of the sleeve valve 56. Obviously, if ring friction were not equal to the downward pressure of the air on' the top of the plate 89, a firm contact between the plate 89 andthe top of the valve sleeve 56 could not be secured nor maintained. The cam means insures that the sleeve 56 will always be supported against movement by thepressure of the plate 89 during the compression. stroke and, as a result, the pressure betweenthe plate 89'and the top of the valve sleeve 56 may be made as high as found desirable to make this joint tight. i

The head casting 15 has for each cylinder a discharge passageway 91 inthe shape of a frusto-conic'al opening served by a plate check valve 92 and guided by a suitable flange or cylindrical guide 95. This guide is formed on a screw plug 96 inserted in the top of the discharge chamber 86, as is apparent from Fig. 2. Lateral branch passages 97 lead up to a valve seat of annular formation controlled by an annular plate check valve 98 also discharging into the central portion 99 of the discharge valve box 86. The construe tion of the discharge valves for each cylinder is the same.

The piston has a suitable dome or pro jection 100 adapted to fit closely in the conical discharge passageway 93 so as to d1splacc to a maximum extent and reduce the clearance due to the use of the passageway above re ferred to. The discharge check valve box 86 is separated from the main part of the head 15 and joined thereto only by the necks '101 and 102 for the separate check valves for the respective cylinders. The central part of the box 86 is supported by a web 105 for the sake of strength and also to assist in radiation'of heat. Suitable webs may be formed on the head to join them to the valve boxes for the purpose of strength and also to assist in dissipating heat. The nozzle 85 leads the excess of air discharged by the blower 31 into the plenum box 86 onto the valve box 86 and its connecting webs so as to dissipate heat therefrom to as great an extent as possible.

The gear oil. pump heretofore described has an intake pipe 106 leading down to sub stantially the bottom of the sump 107 formed in the base 13, and by this suct on pipe 106 oil is drawn by the gear pump and discharged into the pipe 44 from whence the lubricating flow is distributed through the. passageways 50 and connected branches. The dome 43 into which the discharge of oil from the gear pump occursis'joined by the pipe 45 to the unloading cylinder 46 and to the pressure controlled release valve cylinder- 47, which has the port 48 and the over running piston valve 108 normally pressed downto over run the port 48 by means of the coil compression spring 109. A release passageway 110 leads from the cylinder 47 to the valve box 111, which valve box has the control valve 10 therein. The control valve 10 has a stem 112 projecting in line with the stem or rod 113 of the unloading control piston 9. The valve 10 is normally applied to its seat by a compression spring 114 except when the piston 9 is depressed by air admitted by the regulator 5.

crates pressure, the oil will be driven to the bearings and, at the same time, oil is driven through the pipe 45 into the cylinder 46 and into the cylinder 47. Assume that the valve 10 is closed in the valve chamber 111, pressure builds up in the oil system first raising the piston 7 8 in the cylinder 46, raising the pivot pin 74 so that reciprocation of the lever 55 applies the sleeves 56 and 82 alternately to their seats under the head 15 for their compression strokes and then alternately lowers them for the suction strokes. The cam on the crank shaft 16 is so arranged as to close one sleeve valve and open the other at the center point, that is to say, when one piston is down and the other up, or vice versa.

After the pressure of oil has raised the piston 7 8 against its upper stop so as to bring the sleeve valves into their operating range of action, further accumulation of pressure in the system raises the piston 108, uncovering the release port 48, so that the oil dis charged at the port 48 is released only under a predetermined pressure.

Assume, in Fig. 2, that the piston 55 is starting upward from lower dead center and that the shaft 16 is turning in a clockwise direction as viewed in Fig. 4, the cam 73 raises the sleeve 56 with the first upward motion of the piston to apply the sleeve and hold it against its seat 89.

This work of raising the sleeve the slight distance required to close the upper end of the sleeve might all be performed by ring friction, and likewise the work of lowering the sleeve 82 might all be performed by ring friction, in which event the cam operated mechanism" would have merely to'follow the natural movement of the cylinders and lock them in their position. This, normally, is the ease. The compression of gas in the sleeve 56 acts upon the top side of the sealing plate or seat 89 tohold the oint tight. The air is driven out to the ports controlled by the valves 94 and 98 into the central chamber 99 and from thence into the discharge pipe 2 and to the receiver 3, or to the delivery main 4.

The cooling system for cooling the gases in the discharge valve chamber described in my co-pending application Serial No. 180,433, filed April 2, 1927, may be used in conjunc tion with the present construction if desired. Also, I wish to point out that the combined intake and discharge valve construction shown in my co-pending application Serial No. 183,652, filed April 14, 1927, may be used in conjunction with the valve control mechanism 'of the present structure if desired.

Assume that the receiver 3 has been charged to'the predetermined maximum pressure and that the controller 5 thereupon admits live air to the cylinder 8, depressing the piston 9, opening the valve 10, and permitting the pressure in the oil system to escape' The piston 108 first descends under the influence of the springv 109, closing the port 48, but

not closing the passageway 110, so that,

thereafter, continued escape of oil pressure permits the piston 7 8 to move to its lower position under the influence of the spring 81 thereby carrying down the pivot 74, and hence the path of travel or the traverse of the sleeve valves 56 and 82 lies entirely be low the seat 89 on the bottom of the head 15, so that the valvesare not closed even though raised to their uppermost position by the cam mechanism. llhereupon, the compressor is unloaded and may be operated idly until such time as the valve 10 is closed to permit the building up of pressure. It is desirable to retain suflicient oil pressure on the lubricating systenrto lubricate the machine while operating idly.

The cooling ofthe compressor is effected by the air discharged'by the blower 31 to the box or duct 33 into the plenum chamber 86 surrounding the sleeves 56 and 82, cooling these sleeves by the passage of air around them through the discharge conduit 84 and nozzle 85, which nozzle directs the cooling air upon the top of the head 15 and against the discharge valve chamber 86.

While I have shown the lower shaft 37 as driven at a speed approximately twice that of the crank shaft 16, it is to be understood that the gear ratio may be varied in order to secure the desired displacement of air, and to this end the size of the blower 31 may also be controlled. In this case the gears which serve to drive the blower at thehigher rate of speed also form the gear pump for lubricating the compressor and'for feeding the unloader.

I do not intend to be limited to the .details shown and described except as they are declared in the appended claims.

I- claim:

1. In combination, a compressor'having a piston, a cylinder, a sleeve valve, a crank-" shaft for said piston, a cam driven by said shaft, and a camfollower connected to said sleeve, said cam having a dwell for maintaining the valve open, a throw. for closing the valve, a dwell for maintaining the valve closed, and a throw for opening of the valve,

said valve operating for each stroke of the piston.

2. In a compressor, the combination of a cylinder having a head, said head providing a valve seat, a sleeve valve having endwise engagement with said seat, a piston,a crankshaft for operating the piston, eccentric means on the crank-shaft, and means op erated by said eccentric meanson the crankshaft and connected to said sleeve valve to hold said valve in closed position during the compression stroke of the piston.

3. In a compressor, the combination of a cylinder, a movable sleeve valve therein, a

piston in-said sleeve, a crank-shaft connected to said piston, said shafthaving an eccentric member, a thrust rod operated by said eccentric member and connected to said sleeve valve for holding said sleeve valve stationary in closed position during the compression stroke of the piston.

4. In a compressor, the combination of a cylinder, a sleeve valve, a piston, a crankshaft connected to said piston, an eccentric member on the crank-shaft, a pivoted arm connected to said sleeve valve, means operated by the eccentric member and connected to said arm for holding said valve sleeve stationary in closed position during the compression stroke of the piston.

5. In a compressor, the combination of a cylinder, a sleeve valve, a piston, a crank shaft connected to said piston, an eccentric member on the crank-shaft, a pivoted arm connected to said sleeve valve, means operated by the eccentric member and connected to said arm for holding said valve sleeve in closed position during the compression stroke of the piston, andmeans for shifting the pivotal point of said arm to unload the compress sor. V

6. In a compressor, the combination of a cylinder, a valve sleeve in said cylinder, a piston in the sleeve, a'pneumatic seal coopcrating with the sleeve to form a closure for the sleeve, said sleeve being moved into contact with the seal by friction of the piston in the sleeve, and means holding said sleeve in contact with said seal during the compression stroke of said piston.

7. In a compressor, the combination of a cylinder, a valve sleeve in said cylinder, a

piston in the sleeve, a crank-shaft for operating said piston, a seat adapted to be engaged by the valve sleeve to close the same, said sleeve being adapted to be moved to seat by the frictionofthe piston therein, and means independent of the aforesaid friction for holding said valve to seat during the compression stroke of the piston.

8. In a compressor, the combination of a cylinder, a piston, a crank-shaft for recipro'cating the piston in the cylinder, an inlet valve, a pivoted arm connected to said valve, a cam on said crank-shaft, and a follower connected to said arm for operating said valve. 9. In a compressor, the combination of a cylinder, a piston, a crank-shaft for reciprocating the piston in the cylinder, an inlet valve, a pivoted arm connected to said valve, a. cam on said crank-shaft, a follower connected to said. arm-for operating said valve, and an unloader for shifting the pivotal point of said arm to unload the compressor.

10. In a compressor, the combination of a cylinder, a straight cylindrical valve sleeve,

and a head having a yielding plate secured at its outer margin on the head and forming a seat along its inner margin for the end of saidsleeve.

11. In a compressor, the combination of a cylinder, a straight cylindrical valve sleeve, a head having a yielding plate forming a seat for the end of said sleeve, said plate being pressed into engagement with the end of the sleeve by pneumatic pressure to form a seal,

and means to hold the sleeve positively against said plate.

12. In a compressor, the combination of a cylinder, a straight cylindrical valve sleeve, a head having a yielding plate forming a seat for the end of said sleeve, said plate being pressed into engagement with the end of the sleeve by pneumatic pressure to form a seal, means to hold the sleeve positively againstsaid plate, and unloading means for disabling said positive holding means.

13. In a compressor, the combination of a cylinder, a straight cylindrical valve sleeve, a head having a yielding plate forming a seat for the end of said sleeve, and a ring clamping said plate to said head and forming a guide for the upperend of said sleeve.

14. In a compressor, a cylinder, a piston therefor, a crank-shaft for the piston, a single reciprocating sleeve valve for the cylinder, and a connection between the sleeve valve and the crank-shaft for reciprocating said sleeve valve, the motion of the sleeve valve being al ways in the same direction as the piston.

15. In a compressor, a hollow cylinder frame-casting forming a plenum box, said casting having a transverse web at the inner end, a head closing the casting at the outer end, a cylindrical sleeve having a guide hearing at itsinner end on said web, a guide bearing at the bottom of the head for guiding the outer end of the sleeve, a valve seat on the head for the upper end of said sleeve, a blower discharging air into said plenum box, said sleeve being exposed to the cooling air in said plenum box throughout substantially its entire length. I

16. In a compressor, a hollow cylinder frame casting forming a plenum box, said casting having a transverse web at the inner end, a head closing the casting at the outer end, a cylindrical sleeve having a guide bearing at its inner end on said web, a guide hearing at the bottom of the head for guiding theouter end of the sleeve, a valve seat on the head for the upper end of said sleeve, a blower discharging air into said plenum box, said sleeve being exposed to the coolingair in said plenum box throughout substantially its entire length, and a valve actuating lever connected to said sleeve and disposed within said plenum box. 7

17. In combination, a head having an annular valve'seat, a sleeve valve guided in alignment with said valve, seat and having a traverse of limited extent, a piston in said sleeve, a crank-shaft having a connecting rod for driving said piston, a rocking lever connected to said sleeve valve, a pivot for said lever, cam controlled means driven by said crank-shaft for rocking said lever, and means for shifting the position of said pivot to change the mean position of the sleeve to control loading and unloading of the compressor.

18. In a compressor, the combination of a crankshaft, a gear mounted upon the crankshaft, a blower having a shaft, said blower being adapted to discharge a blast of cooling air for the compressor, a gear on said blower shaft, a pump housing enclosing said gears and forming a gear pump therewith, said crank-shaft being drilled for forced lubrication, and a duct leading from the pump housing to said drilling in the crank-shaft.

19. In combination, in a compressor, a head having an annular valve seat, a sleeve valve guided in alignment with said valve, seat and having a transverse of limited extent, a piston in said sleeve, a crank shaft having a connecting rod for driving said piston, a rocking lever connected to said sleeve, a pivot for said lever, cam controlled means driven by said crank shaft for rocking said lever, a gear mounted on the crank shaft, a blower for cooling the sleeve valve, said blower having a shaft, a gear on said blower shaft, a pump housing enclosing said gears and forming a gear pump therewith, and an unloader cylinder having a piston adapted to be actuated by oil delivered from said oil pump, said piston being adapted to shift the position of said pivot to change the mean position of the sleeve to control loading and unloading of the compressor.

20. In a compressor, a head having a palr of valve seats on the bottom thereof, a pair of valve sleeves guided in alignment with said valve seats and adapted to be reciprocated towards and from said valve seats, pistons in said sleeves, a lever connected to said sleevesand having a pivot point substantially equi-distant between them, an unloader cylinder, and a piston in said cylinder, said piston being connected to said pivot for shifting the position of the same for loading and unloading the compressor.

21. In a compressor, the combination of a sleeve forming a cylinder and an intake valve, a member forming with said sleeve a cylinder head and an intake valve seat, a crank shaft, a piston operated thereby, means operated by the crank shaft for actuating said intake valve sleeve, and an unloader for rendering said means ineffective to close saidintake valve against said seat.

22. In a compressor, the combination of means acting as a cylinder and having means acting as an intake valve therefor, a piston for the cylinder, a crank shaft, mechanical valve operating linkage for said second mentioned means, spring means for shifting the linkage into inoperative position torender it incapable of closing the intake valve means, and means controlled by the speed of the crank shaft for shifting said linkage into opmeans, a hydraulic pump operated from the crank shaft, and a hydraulic cylinder filled by said pump When the crank shaft is operated at a predetermined speed for shifting said valve actuating means against said spring into Working position.

24. In a compressor, the combination of means acting as a cylinder and having means acting as an intake valve therefor, a piston for the cylinder, a crank shaft, mechanical valve actuating means for periodically open ing and closing the intake valve means in synchronism With the operation of the crank shaft, resilient means for moving said valve actuating means into unloaded position, said valve actuating means when moved into unloaded position being incapable of closing the intake valve means, and an unloading cylinder having a piston for overcoming said resilient means to move said valve actuating mechanism into position Where it can close the intake valve means.

25. In a compressor, the combination of means acting as a cylinder and having means acting as an intake valve, a crank shaft, a

piston operated thereby, means operated by the crank shaft for actuating said intake valve means, and an unloader for rendering said last named means ineffective to close said intake valve means, said last named actuating means including a rocking lever and an unloade-r for shifting the pivotal point of the lever to render the actuating means ineffective to close the intake valve means. 7

26. In a compressor, the combination of means acting as a cylinder and having means acting as an intake valve, a piston for the cylinder, a crank shaft for actuating the piston, mechanical valve actuating mechanism for the intake valve means acting in synchronism with the crank shaft, means holding" said mechanism in inactive position to prevent closing of the intake valve means, a lubricating pump for the compressor, and a hydraulic cylinder connected to the lubricating pumpffor overcoming said holding means, 7

thereby to render the valve actuating mechanism operative to close the intake valve means.

27. A compressor comprising, in combination, a cylinder, said cylinder operating as an inlet valve, a pivoted rocker arm for actuating the valve, a crank shaft, a piston operating in said cylinder, means connecting the piston and crank shaft, and means responsive to thespeed of the crank shaft for shifting the pivot of the rocker arm.

28. A compressor comprising means acting as a cylinder and having means acting as an inlet valve therefor, a piston operable in the cylinder, means including a pivoted rocker arm for actuating the valve, a crank shaft for the piston, and means responsive to the speedof the crank shaft for shifting the pivot ofthe rocker arm.

29. A compressor comprising means acting as a cylinder and having means acting as an inlet valve therefor, a piston operable in the cylinder, means including a pivoted rocker arm for actuating the valve, a crank shaft for the piston, means responsive to the speed of the crank shaft for shifting the pivot of the rocker arm, and means operating in accordance With the speed of the crank shaft for supplying fluid to said inlet valve means.

In Witness whereof, I hereunto subscribe L my name this 6th day of April, 1927.

BURTON S. AIKMAN. 

